1. Field of the Invention
The present invention relates to a plasma display panel, and more particularly, to a plasma display panel which expands a discharge space and restricts discharge current.
2. Discussion of the Related Art
Generally, a plasma display panel and a liquid crystal display (LCD) have lately attracted considerable attention as the most practical next generation display of flat panel displays. In particular, the plasma display panel has higher luminance and a wider viewing angle than the LCD. For this reason, the plasma display panel is widely used as a thin type large display such as an outdoor advertising tower, a wall TV and a theater display.
A related art plasma display panel of three-electrode area discharge type will be described with reference to the accompanying drawings.
FIG. 1 is a perspective view of a related art plasma display panel of three-electrode area discharge type, and FIG. 2 is a structural sectional view of the plasma display panel of FIG. 1.
As shown in FIGS. 1 and 2, the related art plasma display panel of three-electrode area discharge type includes an upper substrate 10 and a lower substrate 20 which face each other. In FIG. 2, the lower substrate 20 is rotated by 90°.
The upper substrate 10 includes a plurality of scan electrodes 16 and 16′, a plurality of sustain electrodes 17 and 17′, a dielectric layer 11, and a protection layer 12. The scan electrodes 16 and 16′ are formed at certain intervals in one direction in parallel to the sustain electrodes 17 and 17′. The dielectric layer 11 is deposited on the scan electrodes 16 and 16′ and the sustain electrodes 17 and 17′.
The lower substrate 20 includes a plurality of address electrodes 22 formed at certain intervals in one direction(orthogonal to the scan electrodes and the sustain electrodes) in parallel to one another, a dielectric film 21 formed on an entire surface of the substrate including the address electrodes 22, a plurality of barriers 23 formed on the dielectric film 21 between the respective address electrodes, and a phosphor 24 formed on surfaces of the barriers 23 in each discharge cell and of the dielectric film 21.
Inert gases such as He and Xe are mixed in a space between the upper substrate 10 and the lower substrate 20 at a pressure of 400 to 500 Torr. The space forms a discharge area.
The scan electrodes 16 and 16′ and the sustain electrodes 17 and 17′ are of transparent electrodes and bus electrodes of metals so as to increase optical transmitivity of each discharge cell, as shown in FIGS. 3 and 4. That is to say, the electrodes 16 and 17 are of transparent electrodes while the electrodes 16′ and 17′ are of bus electrodes.
A discharge voltage from an externally provided driving integrated circuit(IC) is applied to the bus electrodes 16′ and 17′. The discharge voltage applied to the bus electrodes 16′ and 17′ is applied to the transparent electrodes 16 and 17 to generate discharge between the adjacent transparent electrodes 16 and 17. The transparent electrodes 16 and 17 have an overall width of about 300 μm and are made of indium oxide or tin oxide. The bus electrodes 16′ and 17′ are formed of a three-layered thin film of Cr—Cu—Cr. At this time, the bus electrodes 16′ and 17′ have a line width of ⅓ of a line width of the transparent electrodes 16 and 17.
The operation of the aforementioned AC type plasma display panel of three-electrode area discharge type will be described with reference to FIGS. 5a to 5d. 
If a driving voltage is applied between each address electrode and each scan electrode, opposite discharge occurs between the address electrode and the scan electrode as shown in FIG. 5a. The inert gas injected into the discharge cell is instantaneously excited by the opposite discharge. If the inert gas is again transited to the ground state, ions are generated. The generated ions or some electrons of quasi-excited state come into collision with a surface of the protection layer as shown in FIG. 5b. The collision of the electrons secondarily discharges electrons from the surface of the protection layer. The secondarily discharged electrons come into collision with a plasma gas to diffuse the discharge. If the opposite discharge between the address electrode and the scan electrode ends, wall charges having opposite polarities occur on the surface of the protection layer on the respective address electrode and the scan electrode.
If the discharge voltages having opposite polarities are continuously applied to the scan electrode and the sustain electrode and at the same time the driving voltage applied to the address electrode is cut off, area discharge occurs in a discharge area on the surfaces of the dielectric layer and the protection layer due to potential difference between the scan electrode and the sustain electrode as shown in FIG. 5d. The electrons in the discharge cell come into collision with the inert gas in the discharge cell due to the opposite discharge and the area discharge. As a result, the inert gas in the discharge cell is excited and ultraviolet rays having a wavelength of 147 nm occur in the discharge cell. The ultraviolet rays come into collision with the phosphors surrounding the address electrode and the barrier so that the phosphors are excited. The excited phosphors generate visible light rays, and the visible light rays display an image on a screen. That is, the plasma display panel is operated.
At this time, luminance of the plasma display panel is proportional to discharge current between the scan electrode and the sustain electrode. Accordingly, if the discharge current is great, the screen of the plasma display panel becomes bright. Also, the wider the distance between the scan electrode and the sustain electrode is, the higher luminance of the plasma display panel is. This is because that the discharge distance between the electrodes increases so that ultraviolet rays in a positive column region are generated.
A white colored screen displayed by the plasma display panel is determined by luminance ratio of a red discharge cell, a green discharge cell and a blue discharge cell. At this time, picture quality of the white colored screen becomes clearer if a color temperature is high.
However, since the related art plasma display panel has lower luminance than that of a discharge tube such as a fluorescent lamp and a neon lamp, it is not sufficient for a next generation display device to substitute a CRT. This is because that the discharge cell formed in the related art plasma display panel has a short distance between the discharge electrodes as compared with a discharge tube such as a neon lamp and a fluorescent lamp, thereby resulting in that ultraviolet rays in a positive column region having good light-emitting efficiency are not utilized.
Furthermore, the related art plasma display panel has a problem that picture quality of a white colored screen is poor because the luminance ratio of the red discharge cell, the green discharge cell and the blue discharge cell is different.